1. Field of the Invention
The present invention relates to a sleeve type casing head adapter to be attached to a casing, and more particularly to a reusable sleeve type casing head adapter.
2. General Background of the Invention
In the oil industry, when drilling a deep well, it is customary to begin by installing a relatively short length of casing, the top of which is connected to a casing head. The casing head is usually slipped onto the upper end of the casing, the upper end of the casing is welded along its periphery to the inner surface of the casing head, and the lower end of the casing head is welded to the exterior of the casing (before the welding can be done, it is necessary to pre-heat the casing head and the casing at the points to be welded, as is well known in the art). Ideally, these welds secure the casing to the casing head and prevent fluid migration and pressure loss between the exterior of the casing and the interior of the casing head. After the welds have cooled, a test is performed to determine if any leaks exist. If not, the installation of the equipment proceeds. If there are leaks, the casing head is rewelded.
If the well is not brought to production completion, the casing is normally cut below the casing head and is sent to a machine shop to have a "Dutchman" (i.e., a piece of pipe welded onto the casing head) machined out of the casing head in an effort to salvage the casing head. This is an expensive and time consuming task.